1. Field of the Invention
The present invention relates to a self-expandable medical instrument for treating defects in a patient's heart, in particular for the transvascular implantation of a prosthetic heart valve, whereby the medical instrument can be introduced via a catheter system into the patient's body in a minimally-invasive procedure. In particular, the invention relates to a device for the transvascular replacement of diseased heart valves.
2. Background Information
A device of this type is known in principle to medical technology. At present, biological or mechanical valve models are available to substitute for human heart valves which are usually fixedly sewn into the bed of the heart valve during a surgical procedure through an opening in the thorax after removal of the diseased heart valve. In this surgical procedure, the patient's circulation must be maintained by a heart-lung machine, whereby cardiac arrest is induced during the implantation of the prosthetic heart valve. This consequently makes the surgical procedure a risky one coupled with the associated risks for the patients and a lengthy post-operative treatment phase. In particular, the risks of such a surgical procedure are often no longer justifiable in the case of multimorbid patients.
Minimally-invasive treatment procedures of recent development are characterized in particular by the surgery being able to be performed under local anesthesia. One approach provides for implanting a self-expanding stent connected to a collapsible heart valve into the human body by means of an appropriate catheter system. The catheter systems is used to guide such a self-expanding prosthetic heart valve through the inguinal artery or vein to its site of implantation at the heart. After reaching the site of implantation, the stent, consisting for example of a plurality of self-expanding stent segments which can be bent relative one another in its longitudinal direction, can then be successively expanded. Following this expansion, anchoring hooks can for example support the anchoring of the prosthetic heart valve at least in the respective blood vessel close to the heart. The actual prosthetic heart valve itself is thereby in the direct proximal area of the stent.
Known for example from the DE 100 10 074 A1 printed publication is a device for fastening and anchoring prosthetic heart valves, which is essentially formed from wire-shaped interconnected elements. The device thereby provides for using various different arched elements in order to attain a secure fixation of and support for the prosthetic heart valve. To this end, the device described in this printed publication makes use of three identical pairs of arched elements, arranged to be offset from one another by 120°. These arched elements are interconnected by means of solid articulations, whereby the solid articulations fulfill the function of pivot bearings. Additional arched elements bent opposite to each other are furthermore provided which form rocker arms as equal in length as possible in order to achieve a secure placement of the arched elements even when subject to peristaltic actions on the heart and blood vessels and a solid sealing for an implanted and anchored prosthetic heart valve.
In the known solutions, however, there is a risk of heart valve implant malalignment. This essentially relates to the exact positioning and longitudinal orientation of the prosthetic heart valve to be implanted. In particular, it is only with immense skill on the part of the attending surgeon—if at all—that a stent with the prosthetic heart valve at its proximal end winds up being positioned so precisely in the proximity of the patient's diseased heart valve that both sufficient lateral positioning accuracy as well as a suitable longitudinal placement to the prosthetic heart valve can be optimally ensured.
Among other complications, an implantation malalignment of a less than optimally positioned prosthetic heart valve can lead to, for example, leakage or valvular regurgitation, which puts a substantial burden on the ventricle. Should, for example, a prosthetic heart valve be implanted too far above the actual heart valve plane, this can lead to occlusion of the coronary artery origination (coronaries) and thus to a fatal coronary ischemia with myocardial infarction. It is therefore imperative for an implanted prosthetic heart valve to meet all the respective requirements for both the accuracy of the lateral positioning as well as the longitudinal placement.
In conventional implantation techniques in which self-expandable prosthetic heart valves are, for example, guided through a patient's inguinal artery to the site of deployment at the heart in a minimally-invasive procedure, the prosthesis is usually introduced using a guide wire and catheters, whereby conventional balloon catheters can also be used. Although such a surgical introduction can be monitored and controlled, for example with fluoroscopy (Cardiac Catheterization Laboratory=CCL) or with ultrasound (Transesophageal Echocardiogram=TEE), oftentimes—due to the limited maneuverability of the prosthetic heart valve which is still in a collapsed state during the introduction procedure and despite being in the collapsed state is still of relatively large size—it is not possible to ensure the required positioning accuracy and especially the longitudinal placement to the prosthetic heart valve implant with the corresponding anchoring elements affixed thereto. In particular—as a result of a possible coronary artery occlusion—an angle misalignment to the implanted prosthetic heart valve from the optimum site of deployment can pose a threat to the respective patient.
In designing a prosthetic heart valve, special consideration must in particular be given to the substantial forces also acting on the prosthetic during the filling period of the cardiac cycle (diastole), necessitating a secure anchorage in order to prevent the implanted prosthetic heart valve from dislodging.
Hence on the one hand, the prosthetic heart valve must be able to be maneuvered to the greatest extent possible in the respective coronary artery during the implantation procedure so as to ensure optimum positioning accuracy and, on the other hand, the implanted prosthesis must be able to be firmly anchored at its site of implantation in order to effectively prevent subsequent prosthesis misalignment.
The present invention addresses the problem that the known devices for transvascular implantation and fixation of prosthetic heart valves are often not suitable for a simple implantation of a prosthetic heart valve with the required positioning accuracy. Moreover, explanting a previously implanted prosthetic heart valve in a minimally-invasive procedure or accordingly correcting an incorrectly positioned prosthetic heart valve has to date often only been possible with great effort, if at all.
On the basis of the problems as set forth, one task on which the present invention is based is that of providing a device for the transvascular implantation and fixation of prosthetic heart valves which remedies the above-described disadvantages inherent to conventional implantation systems.